Methanol oxidation catalysts



fatented ea. 20, 1949 6 Claims. (Cl. =260--G03) l The invention relatesto the imanufa'oture of .formaldehydelby the catalytic oxidation 'ofmethanol in Which bismuth molybdate is used as a catalyst and: alsorelates toiafprocess ofi preparing 2 which parts are by weight unless=otherw-lse istated.

'Erample JA.- 'A catalyst containing atomic ratios of bis'muth tomolybdenum and sulfur f i h molybdate catalysts. v5 1:55020'3 may i be:pre'hared by "kneading bismuth An object of thegpresent invention'is-to?provide nitrate (hydrated) ammonium molybdate and :improvedcatalysts for the oxidation ofinithanol about 6% water iinxp'rope'rstoichi'ometrical fproto formaldehyde. Another object .isto provide ipoztionsitoigivethis'ratio. The-resulting slurry is suitable methodsfore-preparing 'such a catalyst. ignited =toi45'0" kneaded with 49parts'of 1 :niurther object-is to provide" bismuthlmolyhdate 10 iBaumsulfuricia'eidfperipart of the ignitediprod-.catalystsfor.thezvaportphasetoxidationirofimethuet f anii dried at i150The catalyst has a .anolin the;;presehce of oXyg-en :or airwhiohroata-:densitwdf 3.1:5. lysts:mayuorimayrnot be promoted. yetianotherr-IEmzmpze LBe- A leatalyst having "an atomic object is to providebismuth molybdate ioatalysts imt t jffbismufl' jEto molybdenum fof 5may/be pr m "wi h lfa 504%) nd ph ph 1 :prepared by kneauin' theiproperstoichiometric (PO4 radicals. -Other"obje'otsrand advantages ip po tm rfgftibismuth zmt t d m n m ofthe invention will'hereinafterfappear. ammyg wq i5% i w t ra s g tmgt The invention is conduote'd in zaecord withits lfhis eatfllystifigsffaidensifiyibf ;2broadestaspectsbypassingvaporized n'iethanol gm fi gt lygt i m t {atomicin the presence of an :oiii'dizing Jgas :eontaining zorftio 6f ut 2.1;lmdlybdenum .1 q ulfur 7 f oxygemair, or? air diluted' with ahin'ert'ga'sfirfto 1 5 {0106 l prepared kneading 1 .1p contact, under carefullycontrolled aiid w'elli 5 t u 3m mp 132m g. a o ig u knownCOl'ldi'lliCMilS, With catalysts Of bismuth r tu i m ra r ub eq t t}y vat molybdate promoted or not with sulfate or phosiisooic -r i aaensitwof phate radicals. These catalysts have been found 25 x i I" tobe articularl well adapted for eatal zingthis Example pamlyst havmg inatomic oxidation reaction giving excellent i ields of :mficafbismuthifiovmolybdevnumiof 1.215 may be f prepared b'y'dissolvin'gammoniummolybdate in olmaldehyde with little or no methanol leakage n .tr. r y t c er at C., and adding the proper stolchioand remarkablybypmduct matmm "medicare-mount "(ifbis'muthnitrate dissolved i.Anytsuitable method may be used foriprep'ar- :4 U hi h H a a .ingtheocatalysts. Fortexample bismuth mblyb- ,t 1 9 g i n at} datemaybeformed by kneadingbismu'th nitrate j F f f 1? e t r P is l ff with a.salt of molybdic acid such as the *am- .WeiP l W FPQP g i e at fb9 450monium salt, and thereafter drying and=igniting i g i e fm i ii 9 I theresulting slurry at a temperature between :25 d-, f ely ih i n an atomm.300 and 500 C. The promoters can be introduced ratio of blsmuth 0molybdenum t sulfur of before or after ignition as atheabid, suehfa'ssul- 1 qf wpijepared by kneading the product of fume, or phosphoric acidor as an ammonium Example D with .066part of sulfuric acid and salt ofthe acid. The addition of the promoters p of water per pa f thatproduct. T is is believed to result in an exchange of phosphate 4rcatalyst has a density 0f or sulfate for molybdate radicals attached tothe These a a ys w u d in a p ss w r in metal. If the addition is madeafter ignition m than l was o id d to f r a d using a the resultingmixture is dried before use. gas ratio of oxidizing gas to methanol of10 to 1 The examples illustrate preferred catalysts in on a weightbasis.

Catalyst tests Conversion Catalyst No. Atomic Ratio Furnace'l InletT HotSpot 110110 00, HCOOH C'. C. C'. Percent Percent 312 333 440 82 s 310302 455 as 5 .14 299 2'18 455 90 e .04. 265 261 463 84 7 295 323 465 86a .04

While the above examples illustrate operation with 8.5% oxygen innitrogen as the oxidizing gas, the catalysts of this invention maylikewise be used with inlet gas containing 10.9% oxygen or less.Moreover, the gas to methanol ratio may range from 6 to 1 on a molarbasis up to, for example 30 to 1. If air is used as the oxidizing gas,the ratios may range from 14 to 1 up to 30 to 1. Space velocities mayvary over a wide range and are preferably held between 200 and 50,000hr.- based on methanol. Temperatures within the cataylst bed may rangebetween 200 and 550 C. and are preferably held between 250 and 450 C.

The catalysts are usually heated prior to use in order to facilitatehandling and to eliminatefiuctuations in composition which may resultduring the initial stages of a reaction if the catalyst is not soheated. Moreover, the heating step facilitates forming the catalyst intothe particular mesh size most suitable for the particular converteremployed. Accordingly, the catalyst may be heated during preparation toa temperature between 200 and 600 and preferably to a temperatureslightly above that at which it is to be used. It may then be crushed.or screened to size or pelleted in a suitable pelleting machine.

In use, the catalyst is disposed in a suitable reaction converterprovided with adequate means for removing the heat of reaction, amixture of methanol and air or other oxygen-containing gas being passedover the catalyst and the reaction conducted at ranges given above.Operation is generally at atmospheric pressure although elevated orreduced pressure may be employed. Of the catalysts of the typedescribed, conversion of methanol is practically complete at optimumtemperature levels and the product is primarily formaldehyde with smallamounts of carbon monoxide as the principal by-product. At lowertemperatures some methanol may pass through the catalyst unchanged. Ineither case the formaldehyde is separated by usual methods and ifmethanol is present, it is recovered and recycled.

The conditions for the oxidation of methanol to formaldehyde are allshown in the art, and it has been found that the catalysts of thisinvention will catalyze the reaction with excellent results, whenworking under conditions of time, temperature, concentration ofvaporized alcohol in the mixture undergoing reaction at any suitableratio of alcohol to oxygen, which conditions are already known in theart of catalytic oxidation of methanol to formaldehyde.

I claim:

1. In a process for the preparation of formaldehyde by the catalyticoxidation of methanol, the step which comprises passing vaporizedmethanol and an oxidizing gas containing oxygen into contact with abismuth molybdate catalyst at a temperature between 200 and 500 C.

2. In a process for the preparation of formaldehyde by the catalyticoxidation of methanol, the step which comprises passing vaporizedmethanol and an oxidizing gas containing oxygen into contact with abismuth molybdate catalyst at a temperature between 250 and 450 C.

3. In a process for the production of formaldehyde by the catalyticoxidation of methanol, the step which comprises passing vaporizedmethanol and an oxidizing gas containing oxygen into contact with apromoted bismuth molybdate catalyst at a temperature between 200 and 500C.

' 4. In a process for the production of formaldehyde by the catalyticoxidation of methanol, the step which comprises passing at a temperaturebetween 250 and 450 C. vaporized methanol and an oxidizing gascontaining oxygen into contact with a bismuth molybdate catalystpromoted with a radical selected from the group consisting of sulfate(SO4=) and phosphate (POE) radicals.

5. In a process for the production of formaldehyde by the catalyticoxidation of methanol, the step which comprises passing at a temperaturebetween 250 and 450 C. vaporized methanol and an oxidizing gascontaining oxygen into contact with a catalyst of bismuth molybdatecontaining from 1.5 to 5 atoms of molybdenum per atom of bismuth.

6. In a process for the production of formaldehyde by the catalyticoxidation of methanol, the step which comprises passing at a temperaturebetween 250 and 450 C. vaporized methanol and an oxidizing gascontaining oxygen into contact with a bismuth molybdate catalystcontaining 2 atoms of molybdenum and 0.06 atom of sulfur per atom ofbismuth.

ALVIN B. STILES.

file of this patent:

UNITED STATES PATENTS Number Name Date 1,383,059 Bailey et a1 June 28,1921 1,636,952 Graver July 26, 1927 1,722,297 Jaeger July 30, 19291,851,754 Craver Mar. 29, 1932 1,913,404 Meharg June 13, 1933 2,178,761Lazier Nov. 7, 1939 2,320,253 Arnold May 25, 1943

